There are many applications for position or coordinate selection systems such as in data input and output systems and in various control systems.
A notable example of a position selection system is the control rod selection system of a nuclear reactor. Such control rods contain a neutron absorbing material and they are selectively moveable into and out of the nuclear fuel core to control the neutron population and hence the power level of the core. Also, by varying the depth of insertion of the various control rods, the shape of the neutron flux curve can be controlled. An example of a control rod and system is shown in U.S. Pat. No. 3,020,887. A typical nuclear power reactor core may contain 200 or more of such control rods.
In such a control rod system, means are required to sense and indicate the axial position or depth of insertion of each control rod in the core. Such a sensing and indicating system is shown, for example, in U.S. Pat. No. 3,217,307.
Also required, in the control room of the nuclear plant, is a display or map (e.g. a plan view) of the radial positions of the control rods and selection, indicating and control means by which an operator may select a particular control rod and cause its movement into or out of the core as desired.
In a typical system the selection positions of the control rod map are marked or legended with the X-Y coordinates of the control rods and the legends are arranged in columns and rows corresponding to the plan view positions of the control rods in the core.
In a known system a manually operable key or push button is positioned adjacent each selection position and a particular control rod is selected by depressing its associated push button which mechanically closes an electrical switch. Such selection of a control rod energizes a display showing the insertion position of the control rod and enables appropriate controls by which the operator may selectively cause movement of the control rod.
While such known selection systems have well served their purposes, improvement therein is desirable in several respects, for example, as follows: Since it is desirable that many essential displays and controls be available at a single operator position at a control room console, space is at a premium on the panels of such a console. It is desirable to eliminate the array of selection push buttons because they occupy considerable space on the selection map which can otherwise be used to reduce the size of the map and/or to provide display space. It is also desirable to eliminate the manually operable push buttons and their associated electrical contacts for reliability reasons.
Because of the importance of control rod control to reactor safety it is desirable to provide separate and redundant selection and control systems. While duplicates of the electrical and electronic components can be provided with minimum impact on panel space, duplication of the control rod map and push button array would be virtually intolerable. Thus in the past a degree of redundancy has been achieved by providing an additional set of contacts on the push buttons. A more complete separation of the two systems is desirable.
Thus an object of the invention is a compact and reliable selection system. Another object is to eliminate mechanically actuated electrical contacts from a selection system. A further object is a selection system with two separate channels with minimum interaction between channels.